The present invention relates to mechanical seals, and specifically relates to the use of spacer elements suitable for use in mechanical seals for radially and axially positioning selected seal components.
Mechanical seals are employed in a wide variety of mechanical apparatuses to provide a pressure-tight and fluid-tight seal. The mechanical seal is usually positioned about a rotating shaft that is mounted in and protruding from a stationary housing. The seal is usually bolted to the housing at the shaft exit, thus preventing the loss of pressurized fluid from the housing.
Conventional mechanical seals include face type mechanical seals, which include a pair of sealing rings that are concentrically disposed about the shaft, and axially spaced from each other, as described in U.S. Pat. No. 5,725,220, the contents of which are hereby incorporated by reference. The sealing rings each have sealing faces that are biased into sealing contact with each other. Usually, one seal ring remains stationary, while the other ring contacts the shaft and rotates therewith. The mechanical seal prevents leakage of the pressurized process fluid to the external environment by biasing the seal ring sealing faces in sealing contact with each other. The rotary seal ring is usually mounted in a holder, which is disposed in a chamber formed by a gland. The gland is usually centered on the stationary housing and secured thereto.
Conventional mechanical seals, such as cartridge type seals, employ centering mechanisms to radially space selected seal components, such as the gland and/or holder from the shaft of a housing. Conventional methods for centering the gland include using a number of elongated tabs mounted on the exterior or outboard portion of the mechanical seal. The tabs protrude evenly into the gland, thereby centering the shaft and holder.
A drawback of employing conventional centering mechanisms is that they can typically be lost or misplaced. Another drawback of the conventional seals is that the conventional centering mechanisms center the shaft at the outboard end of the seal. In applications where there is a minimal distance between the seal outboard end and an axial obstruction, it is generally difficult to access the centering mechanism. Consequently, it is difficult to center the gland relative to the shaft. Additionally, the tabs can become disengaged from the seal, increasing the likelihood that the tabs can become lost. Further, conventional seals employing centering mechanisms add distance to the overall length of the seal, which can preclude the use of the seal in a number of applications.
Still another drawback of conventional centering mechanisms is that they only provide radial spacing of seal components and do not provide axial spacing of seal components relative to each other. A further drawback of conventional mechanical seals is that there is generally a relatively small radial spacing between the gland and holder of the mechanical seal. This relatively small spacing restricts the ability to circulate, if at all possible, fluid between the gland and the holder, and therefore restricts the ability to cool selected seal components.
The present invention provides a mechanical seal for mounting to a stationary housing that contains a rotating shaft. The mechanical seal employs an inboard mounted spacer element, which can be a separate element or can be integrally formed with one or more seal components, for providing axial and radial spacing between a holder and a gland. The spacer elements hence center the seal components about a shaft. The spacer element in addition to providing selected axial and radial spacing, further promotes or enhances fluid circulation in a process chamber formed between the gland and holder. The process chamber typically houses process fluid from the housing to which the seal is mounted. Circulating the process fluid within the process chamber aids or assists in cooling one or more seal components as well as preventing unwanted particulates present within the process fluid from packing up between one or more of the seal components. Hence, the spacer element of the present invention by promoting or enhancing the circulation of process fluid within the process chamber functions as a continuous flushing system to ensure that unwanted particles do not pack up within the chamber.
The geometry of the inner surface of the gland and the outer surface of the holder can be configured to optimize, promote or enhance the circulation of process fluid within the process chamber.
According to one aspect, a mechanical seal for mounting to a housing containing a rotating shaft is provided. The mechanical seal comprises a gland having an inner surface and a holder having an outer surface and disposed about said shaft in a selected position relative to the gland. The mechanical seal further comprises a spacer element disposed between the gland and the holder during operation of the seal for substantially uniformly separating the holder outer surface from the gland inner surface and for axially positioning the holder in the selected position relative to the gland.
According to another aspect, a mechanical seal for mounting to a housing containing a rotating shaft is provided. The mechanical seal comprises a gland having an inner surface and a holder having an outer surface and disposed about the shaft in a selected position relative to the gland. The gland inner surface is radially spaced from the holder outer surface to define a chamber. A rotatable spacer element is disposed between the gland and the holder for circulating a fluid through the chamber.
According to another aspect, a method for creating a bi-directional axial flow of fluid in a mechanical seal for sealing a housing containing a rotating shaft is provided. The method comprises providing one or more spacer elements, rotatably mounting the spacer elements between a gland having an inner surface and a holder defining an outer surface and disposed about said shaft in a selected position relative to the gland. The inner surface of the gland is radially spaced from the outer surface of the holder to define a chamber. The method further comprises rotating the spacer elements to induce the bi-directional axial flow through the chamber.
According to yet another aspect, a mechanical seal for mounting to a housing containing a rotating shaft is provided. The mechanical seal comprises a gland having an inner surface, a holder having an outer surface and disposed about said shaft in a selected position relative to the gland and a spacer element disposed between the gland and the holder during operation of the seal. The spacer element substantially uniformly separates the holder outer surface from the gland inner surface and axially positions the holder in the selected position relative to the gland. The inner surface of the gland is radially spaced from the outer surface of the holder to define a chamber, and the holder is positioned within said chamber. The spacer element circulates a fluid flow through the chamber.
According to a final aspect a mechanical seal for mounting to a housing containing a rotating shaft is provided. The mechanical seal comprises a gland having an inner surface a holder having an outer surface and disposed about said shaft in a selected position relative to the gland and a spacer element. The spacer element is disposed between the gland and the holder for positioning the holder relative to the shaft and for circulating a process fluid through a chamber defined by the gland inner surface and the holder outer surface.
Other general and more specific objects of the invention will in part be obvious and will in part be evident from the drawings and description which follow.